Enzyme-facilitated transport and separation of organic acids through liquid membranes

A Supported Liquid Membrane Encapsulating a Surfactant-Lipase Complex for the Selective Separation of Organic Acids

We have developed a novel, lipase-facilitated, supported liquid membrane (SLM) for the selective separation of organic acids by encapsulating a surfactant-lipase complex in the liquid membrane phase. This system exhibited a high transport efficiency for 3-phenoxypropionic acid and enabled the selective separation of organic acids due to the different solubilities of the acids in the organic phase and the variable substrate specificity of the surfactant-lipase complex in the liquid membrane phase. We found that various parameters, such as the amount of surfactant-lipase complex in the SLM, the lipase concentration in the receiving phase, and the ethanol concentration in the feed phase, affected the transport behavior of organic acids. The optimum conditions were 5 g L(-1) of the surfactant-CRL complex in the SLM (CRL=lipase from Candida rugosa), 8 g L(-1) of PPL in the receiving phase (PPL=lipase from porcine pancreas), and an ethanol concentration of 50 vol %. Furthermore, we achieved high enantioselective transport of (S)-ibuprofen attributable to the enantioselectivity of the surfactant-CRL complex.

Highly Enantioselective Separation Using a Supported Liquid Membrane Encapsulating Surfactant−Enzyme Complex

We developed a highly enantioselective separation system for the optically active compounds, (S)-ibuprofen and l-phenylalanine, from their racemic mixtures by employing a supported liquid membrane (SLM) encapsulating a surfactant-lipase complex (or a surfactant-alpha-chymotrypsin complex). In the present system, enzymes encapsulated in the liquid-membrane phase effectively drove the enantioselective transport of optically active compounds through the SLM. This novel SLM allowed high enantioselectivity (ee over 91%) in the optical resolution of racemic ibuprofen and phenylalanine.

Transport of organic acids through a supported liquid membrane driven by lipase-catalyzed reactions

We have developed a lipase-facilitated supported liquid membrane. Lipase-catalyzed reactions were coupled with a supported liquid membrane (SLM) to transport organic acids through the SLM. We succeeded in the rational transport of organic acids through the SLM using lipase-catalyzed reactions and observed that there were differences in the transport behavior of various organic acids due to the substrate specificity of lipase. Subsequently, various parameters, such as the alcohol concentration in the feed phase, the pH in each aqueous phase, an organic solvent in the SLM, and the kind of lipase, were investigated. We found that the optimum conditions were 65 vol% alcohol concentration, pH 6.3 in each aqueous phase, isooctane as the liquid membrane phase and Candida rugosa lipase as the esterification biocatalyst.

The versatility of polysorbate 80 (Tween 80) as an ionophore

A number of experiments were performed to illustrate the unusual versatility of Polysorbate 80 (Tween 80) as an ionophore. New ions shown to be transported by it from and to water layers through a model membrane (CH2Cl2) include H3O+, Li+, Pb2+, Co2+, piperidinium ion, guanidinium ion, and Paraquat, while two complex ions resisted transport under the conditions used. "Reverse" transport of lipophilic guests (azobenzene, azulene, ferrocene) from and to organic solvents through water was also promoted by Tween 80, but C60 was not carried. Three water molecules were transported per molecule of KSCN by the Tween.

Enantioseparation using apoenzymes immobilized in a porous polymeric membrane

Chemical separations represent a large portion of the cost of bringing any new pharmaceutical product to the market. Membrane-based separation technologies, in which the target molecule is selectively extracted and transported across a membrane, are potentially more economical and easier to implement than competing separations methods; but membranes with higher transport selectivities are required. Here we describe an approach for preparing highly selective membranes which involves immobilizing apoenzymes within a microporous composite. The apoenzyme selectively recognizes its substrate molecule and transports it across the composite membrane, without effecting the unwanted chemical conversion of the substrate molecule to product. We demonstrate this approach using three different apoenzymes. Most importantly, it can be used to make enantioselective membranes for chiral separations, one of the most challenging and important problems in bioseparations technology. We are able to achieve a fivefold difference between the transport rates of D- and L-amino acids.